Reaction Steps
1-[4-[4-(1-Ethoxycarbonyl-1-methyl-ethoxy)phenyl]butyryl]-2-(3-methoxyphenylmethyl)semicarbazide (4.08 g, 8.65 mmol) was dissolved in ethyl acetate (7.5 mL). Camphorsulfonic acid (2.21 g, 9.51 mmol) was added in one portion and the solution was heated to reflux overnight. The solution was cooled to rt and washed with sat'd aq. NaHCO3 (2×40 mL) followed by 1N HCl (2×40 mL). The organic was concentrated to an oil, which was redissolved in ethyl acetate (40 mL). Amberlyst-15 resin (4.41 g) was added and the mixture was heated to 50° C. and stirred for 4 h. The mixture was then cooled to rt, filtered, concentrated, and purified by column chromatography (SiO2, 9:1 ethyl acetate:hexanes) to afford the title compound as an oil (1.93 g, 49.2%). 1H NMR (DMSO-d6) δ 11.47 (s, 1 H), 7.22 (t, 1 H, J=8 Hz), 7.04 (d, 2 H, J=8 Hz), 6.82 (d, 1 H, J=2 Hz), 6.76 (m, 2 H), 6.68 (d, 2 H, J=2 Hz), 4.73 (s, 2 H), 4.13 (q, 2 H, J=7 Hz), 3.69 (s, 3 H), 2.48 (t, 2 H,. J=8 Hz), 2.36 (t, 2 H, J=8 Hz), 1.80 (quint, 2 H, J=7 Hz), 1.47 (s, 6 H), 1.14 (t, 3 H, J=7 Hz); 13C NMR (DMSO-d6) δ 174.0, 160.0, 155.0, 153.8, 146.7, 139.8, 135.5, 130.2, 129.8, 120.1, 119.5, 113.8, 113.2, 79.2, 61.6, 55.6, 47.8, 34.0, 28.4, 26.2, 25.7, 14.6; IR (CHCl3) 2940, 1692, 1508, 1467 cm−1; Anal. Calcd. for C25H31N3O5: C, 66.21.; H, 6.89; N, 9.26. Found: C, 66.29; H, 6.75; N, 9.19.
